The present invention relates generally to a telescopic screw assembly and more particularly to a telescopic screw assembly with an anti-rotation mechanism.
Injectors deliver specified quantities of drugs or medicine to a patient and typically include a chamber for storing the drug, a needle connected to the chamber through which the drug is delivered, and a plunger which pushes the medicine from the chamber through the needle. One device for pushing the drug through the chamber is a manually activated plunger. The user typically holds the syringe between two fingers and activates or pushes the plunger with a thumb. One drawback of a manually activated plunger is that patients must be relatively dexterous and have the required hand strength to push the plunger themselves. Another apparatus for pushing the plunger through the chamber is a telescopic assembly. A telescopic assembly is generally contained within the syringe or injector and contains a plurality of nested, threaded members which expand via rotation to push the plunger through the chamber. One drawback of a telescopic assembly is that the rotation of the telescopic assembly must be counteracted to ensure that the assembly achieves full extension. Typical approaches to counteract the rotation include a stopper connected to the outer surface of the telescopic screw assembly. However, such features are susceptible to failure and may prevent the injector from delivering a full dose.
The present invention addresses the challenges associated with effectively preventing rotation of at least the center portion of a telescopic screw assembly.